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The circulatory system and hormones
Published in Frank J. Dye, Human Life Before Birth, 2019
Meanwhile, a partition called the septum primum begins to form from the cephalic wall of the atrial region at the level of its compression by the truncoventricular region. This crescent-shaped tissue has its limbs directed over the dorsal and ventral walls of the atrial region toward a constriction in the heart tube (the atrioventricular canal), between the atrial and ventricular regions of the cardiac tube. As the septum primum develops and its opening (the foramen primum) is about to close, a new opening appears in its cephalic region, the foramen secundum. This opening becomes the foramen ovale, an opening that persists between the right and left atria until the time of childbirth (Figure 15.4A).
Percutaneous closure of atrial septal defect and patent foramen ovale
Published in Debabrata Mukherjee, Eric R. Bates, Marco Roffi, Richard A. Lange, David J. Moliterno, Nadia M. Whitehead, Cardiovascular Catheterization and Intervention, 2017
Fabian Nietlispach, Bernhard Meier
The fetal single atrium is divided into a right and left atrium (RA and LA) by the formation of the septum primum (SP). The SP grows from the atrial roof caudal to the endocardial cushion and leaves a communication between the RA and LA above the endocardial cushion—the foramen primum. The foramen primum is slowly overgrown and closes, while more cranially, a second foramen forms inside the SP, the foramen secundum. Later, from the right atrial roof, the septum secundum (SS) extends caudally to the SP, covering the foramen secundum. A slit-like opening remains between the SP and the SS, named the foramen ovale. The foramen ovale closes after birth in the majority of people, but remains patent in 20%-25% of adults (patent foramen ovale, PFO). The region of the foramen ovale is called the fossa ovalis.
Patent foramen ovale closure for secondary prevention of cryptogenic stroke
Published in Expert Review of Cardiovascular Therapy, 2021
Dhaval Kolte, Igor F. Palacios
Approximately at the fifth week of development, a very thin septum primum begins to migrate downward toward the endocardial cushion. The gap in between both structures forms the foramen primum. As the migration of the septum primum continues, apoptotic changes within the septum will originate the foramen secundum. On the right atrial surface of the foramen secundum, a more muscular and thicker septum secundum migrates downward covering the foramen secundum and leaving a small foramen on the bottom of the atrium, the foramen ovale. This structure provides a right-to-left shunt necessary for fetal circulation. After birth, this communication will spontaneously close in approximately 75% of the population [2].